A rare walking fish that was recently declared endangered after not being seen for 22 years has been spotted in the depths of a marine park off Tasmania's rugged south-west coast.
A member of the anglerfish family, the pink handfish has only been spotted in the wild five times, and was last seen by a recreational diver off the coast of the Tasman Peninsula, south-east of Hobart, in 1999.
But during a recent survey of the Tasman Fracture Marine Park, a nationally-protected conservation area the size of Switzerland, to examine coral, rock lobster and striped trumpeter fish, scientists made a discovery they weren't expecting.
"We've been fortunate enough to do a detailed exploration study for Parks Australia … looking at a whole range of fish species and corals and things that live on the bottom out there," Professor Neville Barrett from the Institute of Antarctic and Marine Studies at the University of Tasmania said.
"And as part of it, we've discovered a pink handfish.
Little is known about the pink handfish, but it had been thought it lived in waters between 15 metres to almost 40 metres deep off Tasmania's east coast — an assumption that has since been overturned.
"We've found [the pink handfish] in 120 metres of water, so that's much deeper than it ever has been seen before," Professor Barrett said.
"The last sighting in 1999 was on the Tasman Peninsula at about 20 to 30-odd metres, and the earliest sighting before that was in about 10 metres at the D'Entrecasteaux Channel.
An incidental and significant discovery
To survey the depths of the marine park, researchers used a 'baited underwater video' to attract fish to the area with minimal impact to their habitat.
"Essentially [the cameras] are facing forward to a bait bag that's about a metre in front of them and the fish are attracted to those baits," Professor Barrett said.
"They're a standard approach all around Australia … the fish come in to see what's happening in the baits and we film them with stereo cameras that we can then use to get the size of the fish as well as their presence or absence.
"In the video, the lobsters are quite strongly attracted to the baits ... but in the process it's disturbed a pink handfish that's swam up and towards the cameras, had a bit of a look, and decided it didn't like it very much, and swam out again.
"But in that time it's given us a really great head-on piece of imagery ... to absolutely categorically identify the species and measure its size."
"And if there are any other rare species that are found in those environments … it's quite exciting because it's actually taken within a no-take and highly protected marine park."
Professor Barrett said the pink handfish are "quite small and hard to detect", but are around 15 centimetres in size.
Although the survey of the marine park was done during February and March this year, it wasn't until early October that the pink handfish was sighted.
Hours of footage that was gathered on the expedition required painstaking annotation, a job that fell to IMAS research assistant Ashlee Bastiaansen.
"I was watching one of our rough videos and there was a little fish that popped up on this reef ledge that looked a bit odd, and I had a closer look and you could see its little hands," Ms Bastiaansen said.
"It wasn't until the lobster did crawl up the side and step on it that we could actually see the colours down the side … [the supervisors] sent it off to the people at CSIRO and others at IMAS which gave us an affirmative that it was a pink handfish, which was very exciting news.
"There was one girl on the team who was quite loud and squealing a bit and she was like 'oh my god'.
A brave new world for a little fish
Jason Mundy, assistant secretary for Parks Australia, said the unexpected discovery of the pink handfish was "good news" for the species.
"It means we've found these fish in a larger range of places than we previously knew them to exist, and encouragingly, we found them within an Australian marine park, which is a place that's established to try and protect some key species, including by reducing pressures on them," he said.
Apart from the pink handfish discovery, Mr Mundy said the broader results from the survey were also encouraging.
"The key findings are always to check the health and trend lines have the populations of those key communities in marine parks, and it was encouraging to note from this research that it appears as if the size and abundance of those key species [rock lobster, striped trumpeter, are increasing in the Marine Park, which is excellent news.
"It takes a long time for us to get a clearer picture of what's going on in some of those places, and the signs we've seen from this research are very encouraging that marine parks are having a positive effect to protect some of those key species," he said.
Professor Barrett said he is optimistic that a "modest" population of pink handfish are calling the depths of the marine park home, and that the species may survive it's toughest challenge yet — climate change.
"It certainly suggests that there's a number down there, exactly how many will certainly need a bit of work to find out," he said.
"But there's certainly some confidence that there's a moderate-sized population down there, and that it's quite a viable one because of the cooler waters that we find down there at present, and are likely to persist for some time."
Professor Barrett is hopeful with additional research, the pink handfish's endangered listing could be reconsidered.
"If we're able to go out there and actually find that this population is quite a significant one, it might actually allow us to delist this species," he said.
"It's always a really wonderful thing to be able to do that, rather than to be nominating species to be listed … if you got to add something, it usually means there is a problem that needs addressing.